#include <cstdlib>
#include <fstream>
//#include <iostream>
#include <cassert>

using namespace std;

#define MAX_N 1001
#define MAX_H 1001
#define UNDEF -1

int N;
int H[MAX_N];
int C[MAX_N];
int mem[MAX_N][MAX_H+2];

int torri_din() {

  for(int i=N-1; i>=0; i--)
    for(int h=MAX_H; h>=0; h--)
      if (H[i] >= h)
        mem[i][h] = C[i] + mem[i+1][h];
      else
        mem[i][h] = min(
          C[i] + mem[i+1][h],
          mem[i+1][H[i]]);
  return mem[0][MAX_H];
}

int main() {

  ifstream fin("input.txt"); 
  assert(fin);
  fin >> N;
  for(int i = 0; i < N; i++)
    fin >> H[i] >> C[i];
  fin.close();
  ofstream fout("output.txt"); 
  assert(fout);
  fout << torri_din();
  fout.close();
  return 0;
}